Password for excel file

I need help putting passwords on documents, i.e. these documents CANNOT be opened unless the password is provided. This could also be for a folder.

Like I have documents in a folder, and I do not want anyone else to have access to this folder, I would therefore like to password protect access to this folder and if possible the files inside.
thanks!
:)

I suppose that might slow down your little sister. Someone who's going to go after your data will (at least) have something as powerful as, say http://lastbit.com/excel/, or any of a number of other excel password cracking tools out there.

I don't know enough about excel or what the password protection actually does, but, considering their history on this, MS isn't exactly confidence inspiring.

Staff: Mentor

If you’re curious: Guaranteed Recovery is the special sort of Brute Force Attack. Formerly in the USA there were serious legislative limitations on the exporting of strong encryption algorithms. Only encryption algorithms with key length up to 40 bit could be exported freely. That’s why Microsoft limited the strength of the Office encryption to 40 bit. Guaranteed Recovery performs a brute force attack on the internal 40 bit key instead of the original password. The 40 bit key length means that there are only 2^40 (about a trillion) possible combinations. It is possible to test them all in a reasonable amount of time.

If your concern is protecting confidential documents from theft, the best approach is to not save them on a laptop at all. Confidential documents should be stored on a computer or server with restricted access.